Compositions and applications of three component benzo[1,2-B:4,5-B] dithiophene-thienothiophene randomly substituted polymers for organic solar cells

ABSTRACT

A polymer having two different sets of repeat units consisting essentially of: 
     
       
         
         
             
             
         
       
     
     Additionally, in the polymer R1 can be selected from the group consisting of alkyl group, alkoxy group, aryl groups and combinations thereof. In the polymer, n and m can be greater than 1. 
     In the polymer, x and y can be different from each other and independently selected from the group consisting of: an alkoxy group, a substituted alkoxy group, an aryl group, an alkyl group, a substituted alkyl group, 
                         
where y=1-3,
 
                         
where y=0-12,
 
                         
where R2 is selected from the group consisting of H, alkyl groups, and aryl groups,
 
                         
where R3 is selected from the group consisting of H, alkyl groups, and aryl groups,
 
                         
where R4 and R5 are independently selected from the group consisting of H, alkyl groups, and aryl groups, —NR 6 R 7  where R6 and R7 are independently selected from the group consisting of H, alkyl groups, and aryl groups.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application which claims thebenefit of and priority to U.S. Provisional Application Ser. No.62/005,178 filed May 30, 2014, entitled “Compositions and Applicationsof Three Component Benzo[1,2-B:4,5-B]Dithiophene-ThienothiopheneRandomly Substituted Conjugated Polymers for Organic Solar Cells,” whichis hereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

FIELD OF THE INVENTION

This invention relates to compositions and applications for a threecomponent benzo[1,2-b:4,5-b]dithiophene-thienothiophene polymer.

BACKGROUND OF THE INVENTION

Solar energy using photovoltaic effect requires active semiconductingmaterials to convert light into electricity. Currently, solar cellsbased on silicon are the dominating technology due to their highconversion efficiency. Recently, solar cells based on organic materialsshowed interesting features, especially on the potential of low cost inmaterials and processing. Judging from the recent success in organiclight emitting diodes based on a reverse effect of photovoltaic effect,organic solar cells are very promising.

Organic photovoltaic cells have many potential advantages when comparedto traditional silicon-based devices. Organic photovoltaic cells arelight weight, economical in the materials used, and can be deposited onlow cost substrates, such as flexible plastic foils. However, organicphotovoltaic devices typically have relatively low quantum yield (theratio of photons absorbed to carrier pairs generated. This is, in part,thought to be due to the second order nature of the intrinsicphotoconductive process. That is, carrier generation requires excitongeneration, diffusion and ionization. The diffusion length of an excitonis typically much less than the optical absorption length, requiring atrade off between using a thick, and therefore resistive, cell withmultiple or highly folded interfaces, or a thin cell with a low opticalabsorption efficiency.

Conjugated polymers are polymers containing π-electron conjugated unitsalong the main chain. They can be used as active layer materials forsome types of photo-electric devices, such as polymer light emittingdevices, polymer solar cells, polymer field effect transistors, etc. Aspolymer solar cell materials, conjugated polymers should possess someproperties, such as high mobility, good harvest of sunlight, goodprocessibility, and proper molecular energy level. Some conjugatedpolymers have proven to be good solar cell materials. Conjugatedpolymers are made of alternating single and double covalent bonds. Theconjugated polymers have a δ-bond backbone of intersecting sp² hybridorbitals. The p_(z) orbitals on the carbon atoms overlap withneighboring p_(z) orbitals to provide π-bonds. The electrons thatcomprise the π-bonds are delocalized over the whole molecule. Thesepolymers exhibit electronic properties similar to those seen ininorganic semiconductors. The semiconducting properties of thephotovoltaic polymers are derived from their delocalized it bonds. Thesubstituents of the polymers also largely influence the electronicproperties. The optical bandgap, mobility and thin-film morphology areaffected by both the type of functional group used as a substituent andthe bulkiness and length of the side chain. Polymers which have onlyminor differences in the side chains will have large differences in thedevice performance.

There is a need in the art for polymer solar cells that exhibitincreased solar conversion efficiency.

BRIEF SUMMARY OF THE DISCLOSURE

A polymer having two different sets of repeat units consistingessentially of:

Additionally, in the polymer R1 can be selected from the groupconsisting of alkyl group, alkoxy group, aryl groups and combinationsthereof. In the polymer, n and m can be greater than 1.

In the polymer, x and y can be different from each other andindependently selected from the group consisting of: an alkoxy group, asubstituted alkoxy group, an aryl group, an alkyl group, a substitutedalkyl group,

where y=1-3,

where y=0-12,

where R2 is selected from the group consisting of H, alkyl groups, andaryl groups,

where R3 is selected from the group consisting of H, alkyl groups, andaryl groups,

where R4 and R5 are independently selected from the group consisting ofH, alkyl groups, and aryl groups, —NR₆R₇ where R6 and R7 areindependently selected from the group consisting of H, alkyl groups, andaryl groups.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and benefitsthereof may be acquired by referring to the follow description taken inconjunction with the accompanying drawings in which:

FIG. 1 depicts a current-voltage diagram of a solar cell

DETAILED DESCRIPTION

Turning now to the detailed description of the preferred arrangement orarrangements of the present invention, it should be understood that theinventive features and concepts may be manifested in other arrangementsand that the scope of the invention is not limited to the embodimentsdescribed or illustrated. The scope of the invention is intended only tobe limited by the scope of the claims that follow.

“Alkyl,” as used herein, refers to an aliphatic hydrocarbon chains. Inone embodiment the aliphatic hydrocarbon chains are of 1 to about 100carbon atoms, preferably 1 to 30 carbon atoms, more preferably, 1 to 20carbon atoms, and even more preferably, 1 to 10 carbon atoms andincludes straight and branched chains such as methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, isopentyl,neo-pentyl, n-hexyl, and isohexyl. In this application alkyl groups caninclude the possibility of substituted and unsubstituted alkyl groups.

“Alkoxy,” as used herein, refers to the group R—O— where R is an alkylgroup of 1 to 100 carbon atoms. In this application alkoxy groups caninclude the possibility of substituted and unsubstituted alkoxy groups.

“Aryl” as used herein, refers to an optionally substituted, mono-, di-,tri-, or other multicyclic aromatic ring system having from about 5 toabout 50 carbon atoms (and all combinations and subcombinations ofranges and specific numbers of carbon atoms therein), with from about 6to about 10 carbons being preferred. Non-limiting examples include, forexample, phenyl, naphthyl, anthracenyl, and phenanthrenyl. Aryl groupscan be optionally substituted with one or with one or more Rx. In thisapplication aryl groups can include the possibility of substituted arylgroups, bridged aryl groups and fused aryl groups.

The present embodiment describes a polymer with only two different setsof repeat units.

In this polymer R1 can be selected from alkyl groups, alkoxy groups andaryl groups and n and m are greater than 1. x and y are different fromeach other and independently selected from the group of: a) an alkoxygroup, b) an aryl group, c) an alkyl group, d)

where y=1-3, e)

where y=0-12, f)

where R2 is selected from the group consisting of H, alkyl groups, andaryl groups f)

where R3 is selected from the group consisting of H, alkyl groups, andaryl groups, j)

where R4 and R5 are independently selected from the group consisting H,alkyl groups, and aryl groups g) —NR₆R₇ where R6 and R7 areindependently selected from the group consisting of H, alkyl groups, andaryl groups.

In one embodiment, the polymer is regio-random. In another embodimentthe polymer is regio-regular.

In one embodiment, the two sets of repeat units can be abenzo[1,2-b:4,5-b′]dithiophene with a 2-ethylhexyl substituted3-fluorothieno[3,4-b]thiophene and a benzo[1,2-b:4,5-b′]dithiophene witha propyl substituted 3-fluorothieno[3,4-b]thiophene. In anotherembodiment, the two sets of repeat units can be abenzo[1,2-b:4,5-b′]dithiophene with a 2-ethylhexyl substituted3-fluorothieno[3,4-b]thiophene and a benzo[1,2-b:4,5-b′]dithiophene witha propyl substituted 3-fluorothieno[3,4-b]thiophene in a ratio of around50:50. In yet another embodiment, the two sets of repeat units can be a2-ethyl-1-(3-fluorothieno[3,4-b]thiophen-2-yl)hexan-1-one and a1-(3-fluorothieno[3,4-b]thiophen-2-yl)butan-1-one in a ratio of around50:50.

Typically, the number average molecular weight of the polymers is in therange of approximately 1000 to 1,000,000, with ideal polymers having anumber average molecular weight in the range of about 5000 to 500,000,and some ideal polymers having a number average molecular weight in therange of approximately 20,000 to 200,000. It will be appreciated thatmolecular weight can be varied to optimize polymer properties and theinventions of the present disclosure cover all molecular weights. Forexample, lower molecular weight can ensure solubility, while a highermolecular weight can ensure good film-forming properties.

In one embodiment, the ratio of

in the polymer is around 50:50.

The polymers produced from the present disclosure can be used asphotovoltaic materials or active layer material in photovoltaic deviceor electronic devices such as photodetector devices, solar cell devices,and the like. Photovoltaic devices, including polymer solar cell devicesor photodetector devices, are generally comprised of laminates of asuitable photovoltaic material between a hole-collecting electrode layerand an electron-collecting layer. Additional layers, elements or asubstrate may or may not be present. Examples of electronic devices canbe field effect transistors, light emitting devices, and sensors,electrochromic devices and capacitors

EXAMPLES

List of acronyms used:

BDT: Benzo[1,2-b:4,5-b′]dithiophene

FTT: 3-Fluorothieno[3,4-b]thiophene

FTT(E): 2-ethylhexyl 3-fluorothieno[3,4-b]thiophene-2-carboxylate

FTT(P): propyl 3-fluorothieno[3,4-b]thiophene-2-carboxylate

FTT(M): methyl 3-fluorothieno[3,4-b]thiophene-2-carboxylate

FTT (K1): 2-ethyl-1-(3-fluorothieno[3,4-b]thiophen-2-yl)hexan-1-one

FTT (K2): 1-(3-fluorothieno[3,4-b]thiophen-2-yl)butan-1-one

PCE: power conversion efficiency

Jsc: short circuit current

Voc: open circuit voltage

PDI: polydispersity index

M_(n): number average molecular weight defined by (ΣNiMi)/ΣNi where Miis the molecular weight of a chain and Ni is the number of chains ofthat molecular weight

Soxhlet Extraction: The polymer is washed using a reflux apparatus withdifferent solvents. The solvent and polymer is then heated till thesolvent evaporates into a gas, then cools into a liquid. The solvent isthen evaporated off and polymer products are produced.

Example 1

P(BDT-FTT(P)), (100% FTT(P)): Monomers BDT (0.228 g, 0.252 mmol) andFTT(P) (0.101 g, 0.251 mmol) were combined in a Schlenk flask withPd(PPh₃)₄ (14 mg), toluene (10 mL) and dimethylformamide (4 mL). Thesolution was heated to 130° C. and stirred for 36 h. The solution waspoured into 100 mL methanol and the polymer was collected by filtration.The polymer was purified by Soxhlet extraction by washing subsequentlywith acetone, hexanes and chloroform. The polymer was recovered in thechloroform fraction (M_(n)=40 kDa and PDI=2.08).

Example 2

P((BDT-FTT(P))_(0.7)-(BDT-FTT(E))_(0.3)), (70% FTT(P), 30% FTT(E)):Monomers distannyl-BDT (0.142 g, 0.157 mmol), dibromo-FTT(E) (0.022 g,0.047 mmol) and dibromo-FTT(P) (0.044 g, 0.109 mmol) were combined in aSchlenk flask with Pd(PPh₃)₄ (12 mg), toluene (7 mL) and DMF (2.5 mL).The solution was heated to 130° C. and stirred for 24 h. The solutionwas poured into 100 mL methanol and the polymer was collected byfiltration. The polymer was purified by Soxhlet extraction by washingsubsequently with acetone, hexanes and chloroform. The polymer wasrecovered in the chloroform fraction (M_(n)=17 kDa and PDI=3.70).

Example 3

P((BDT-FTT(P))_(0.5)-(BDT-FTT(E))_(0.5)), (50% FTT(P), 50% FTT(E)):Monomers distannyl-BDT (0.108 g, 0.119 mmol), dibromo-FTT(E) (0.028 g,0.059 mmol) and dibromo-FTT(P) (0.024 g, 0.059 mmol) were combined in aSchlenk flask with Pd(PPh₃)₄ (7 mg), toluene (6 mL) and DMF (2 mL). Thesolution was heated to 130° C. and stirred for 24 h. The solution waspoured into 100 mL methanol and the polymer was collected by filtration.The polymer was purified by Soxhlet extraction by washing subsequentlywith acetone, hexanes and chloroform. The polymer was recovered in thechloroform fraction (M_(n)=34 kDa and PDI=3.17).

Example 4

P((BDT-FTT(P))_(0.3)-(BDT-FTT(E))_(0.7)), (30% FTT(P), 70% FTT(E)):Monomers distannyl-BDT (0.080 g, 0.088 mmol), dibromo-FTT(E) (0.029 g,0.061 mmol) and dibromo-FTT(P) (0.011 g, 0.027 mmol) were combined in aSchlenk flask with Pd(PPh₃)₄ (5 mg), toluene (6 mL) and DMF (3 mL). Thesolution was heated to 130° C. and stirred for 36 h. The solution waspoured into 100 mL methanol and the polymer was collected by filtration.The polymer was purified by Soxhlet extraction by washing subsequentlywith acetone, hexanes and chloroform. The polymer was recovered in thechloroform fraction (M_(n)=63 kDa and PDI=2.96).

Example 5

P((BDT-FTT(P))_(0.1)-(BDT-FTT(E))_(0.9)) (10% FTT(P), 90% FTT(E)):Monomers distannyl-BDT (0.093 g, 0.103 mmol), dibromo-FTT(E) (0.044 g,0.093 mmol) and dibromo-FTT(P) (0.004 g, 0.010 mmol) were combined in aSchlenk flask with Pd(PPh₃)₄ (6 mg), toluene (6 mL) and DMF (2 mL). Thesolution was heated to 130° C. and stirred for 24 h. The solution waspoured into 100 mL methanol and the polymer was collected by filtration.The polymer was purified by Soxhlet extraction by washing subsequentlywith acetone, hexanes and chloroform. The polymer was recovered in thechloroform fraction (M_(n)=24 kDa and PDI=2.08).

Example 6

P(BDT-FTT(E)), (100% FTT(E)): Monomers distannyl-BDT (0.115 g, 0.127mmol)) and dibromo-FTT(E) (0.060 g, 0.127 mmol) were combined in aSchlenk flask with Pd(PPh₃)₄ (7 mg) in toluene (4 mL) and DMF (1 mL).The solution was heated to 115° C. and stirred for 96 h. The solutionwas poured into 100 mL methanol and the polymer was collected byfiltration. The polymer was purified by Soxhlet extraction by washingsubsequently with acetone, hexanes and chloroform. The polymer wasrecovered in the chloroform fraction (M_(n)=24 kDa and PDI=2.1).

Example 7

P((BDT-FTT(E))_(0.25)-(BDT-FTT(K1))_(0.75)): Monomers distannyl-BDT(0.10 g, 0.11 mmol)), dibromo-FTT(E) (13 mg, 0.0275 mmol) anddibromo-FTT(K1) (36.5 mg, 0.0825 mmol) were combined in a Schlenk flaskwith Pd(PPh₃)₄ (12.8 mg) in toluene (4.4 mL) and DMF (1.1 mL). Thesolution was heated to 120° C. and stirred for 48 h. The solution waspoured into 100 mL methanol and the polymer was collected by filtration.The polymer was purified by Soxhlet extraction by washing subsequentlywith acetone, hexanes and chloroform. The polymer was recovered in thechloroform fraction (M_(n)=41 kDa and PDI=2.9).

Example 8

P((BDT-FTT(E))_(0.5)-(BDT-FTT(K1))_(0.5)) Monomers distannyl-BDT (100mg, 0.11 mmol)), dibromo-FTT(E) (26 mg, 0.055 mmol) and dibromo-FTT(K1)(24 mg, 0.055 mmol) were combined in a Schlenk flask with Pd(PPh₃)₄ (13mg) in toluene (4.4 mL) and DMF (1.1 mL). The solution was heated to120° C. and stirred for 48 h. The solution was poured into 100 mLmethanol and the polymer was collected by filtration. The polymer waspurified by Soxhlet extraction by washing subsequently with acetone,hexanes and chloroform. The polymer was recovered in the chloroformfraction (M_(n)=29.6 kDa and PDI=2.9).

Example 9

P((BDT-FTT(E))_(0.75)-(BDT-FTT(K1))_(0.25)) Monomers distannyl-BDT (100mg, 0.11 mmol)), dibromo-FTT(E) (39 mg, 0.0825 mmol) and dibromo-FTT(K1)were combined in a Schlenk flask with Pd(PPh₃)₄ (13 mg) in toluene (4.4mL) and DMF (1.1 mL). The solution was heated to 120° C. and stirred for48 h. The solution was poured into 100 mL methanol and the polymer wascollected by filtration. The polymer was purified by Soxhlet extractionby washing subsequently with acetone, hexanes and chloroform. Thepolymer was recovered in the chloroform fraction (M_(n)=20 kDa andPDI=2.43).

Example 10

P((BDT-FTT(E))_(0.5)-(BDT-FTT(K2))_(0.5)) Monomers distannyl-BDT (100mg, 0.11 mmol)), dibromo-FTT(E) (26 mg, 0.055 mmol) and dibromo-FTT(K2)(21 mg, 0.055 mmol) were combined in a Schlenk flask with Pd(PPh₃)₄ (7mg) in toluene (4.4 mL) and DMF (1.1 mL). The solution was heated to120° C. and stirred for 48 h. The solution was poured into 100 mLmethanol and the polymer was collected by filtration. The polymer waspurified by Soxhlet extraction by washing subsequently with acetone,hexanes and chloroform. The polymer was recovered in the chloroformfraction (M_(n)=23 kDa and PDI=1.4).

Example 11

P((BDT-FTT(P))_(0.5)-(BDT-FTT(K1))_(0.5)) Monomers distannyl-BDT (0.185g, 0.21 mmol)), dibromo-FTT(P) (42 mg, 0.10 mmol) and dibromo-FTT(K1)(44 mg, 0.10 mmol) were combined in a Schlenk flask with Pd(PPh₃)₄ (32mg) in toluene (9 mL) and DMF (3 mL). The solution was heated to 120° C.and stirred for 48 h. The solution was poured into 100 mL methanol andthe polymer was collected by filtration. The polymer was purified bySoxhlet extraction by washing subsequently with acetone, hexanes andchloroform. The polymer was recovered in the chloroform fraction(M_(n)=16 kDa and PDI=1.9).

Example 12

Synthesis of P((BDT-FTTM)_(0.25)-(BDT-FTTE)_(0.75)): In a 50 mL Schlenkflask, BDTE (150.0 mg, 0.166 mmol) and FTTE (55.93 mg, 0.118 mmol) andFTTM (14.77 mg, 0.039 mmol) and Pd(PPh₃)₄ (18.3 mg, 0.016 mmol) wereadded. The mixture was vacuumed and backfilled with argon twice before7.5 mL of anhydrous toluene and 1.5 mL of anhydrous dimethylformamidewere added. The solution was frozen by liquid nitrogen and thenvacuumed, backfilled with argon and thawed twice before heated to 120°C. for 20 hours. The product was precipitated out in 40 mL methanol andpurified by Soxhlet extraction, methanol (16 hour), acetone (8 hour),hexane (16 hour) and dichloromethane (4 hour) and then chloroform 2hour. The portion from dichloromethane was the main product (62 mg,yield 43.1%) after precipitated from methanol and then dried overnight.

Example 13

Synthesis of P((BDT-FTTM)_(0.5)-(BDT-FTTE)_(0.5)): In a 50 mL Schlenkflask, BDTE (100.0 mg, 0.106 mmol) and FTTE (24.86 mg, 0.053 mmol) andFTTM (19.69 mg, 0.053 mmol) and Pd(PPh₃)₄ (12.2 mg, 0.011 mmol) wereadded. The mixture was vacuumed and backfilled with Argon twice before7.5 mL of anhydrous toluene and 1.5 mL of anhydrous dimethylformamidewere added. The solution was frozen by liquid nitrogen and thenvacuumed, backfilled with Argon and thawed twice before heated to 120°C. for 20 hours. The product was precipitated out in 40 mL methanol andpurified by Soxhlet extraction, methanol (16 hour), acetone (8 hour),hexane (16 hour) and dichloromethane (4 hour) and then chloroform 2hour. The portion from dichloromethane was the main product (60 and 24mg respectively, yield 60.0%) after precipitated from methanol and thendried overnight.

Example 14

Synthesis of P((BDT-FTTM)_(0.75)-(BDT-FTTE)_(0.25)): In a 50 mL Schlenkflask, BDTE (150.0 mg, 0.166 mmol) and FTTE (18.65 mg, 0.039 mmol) andFTTM (44.3, 0.118 mmol) and Pd(PPh₃)₄ (18.3 mg, 0.016 mmol) were added.The mixture was vacuumed and backfilled with Argon twice before 7.5 mLof anhydrous toluene and 1.5 mL of anhydrous dimethylformamide wereadded. The solution was frozen by liquid nitrogen and then vacuumed,backfilled with Argon and thawed twice before heated to 120° C. for 20hours. The product was precipitated out in 40 mL methanol and purifiedby Soxhlet extraction, methanol (16 hour), acetone (8 hour), hexane (16hour) and dichloromethane (4 hour) and then chloroform 2 hour. Theportion from chloroform was the main product (116 mg, yield 85.5%) afterprecipitated from methanol and then dried overnight.

In closing, it should be noted that the discussion of any reference isnot an admission that it is prior art to the present invention,especially any reference that may have a publication date after thepriority date of this application. At the same time, each and everyclaim below is hereby incorporated into this detailed description orspecification as an additional embodiment of the present invention.

Device Fabrication and Measurement

ZnO sol-gel was prepared by dissolving zinc acetate dihydrate (220 mg, 1mmol) and ethanolamine (62 mg, 1 mmol) into 2-methoxyethanol (2 mL) andstirred for 1 h in air. ITO-coated glass substrates were washed withdetergent (15 min), DI water (2×15 min), acetone (15 min), andisopropanol (15 min) in an ultrasonication bath. The substrates wereplaced in a vacuum oven at 80° C. for 2 h and placed in a UV-ozonecleaner for 15 minutes. After filtration with a 0.2 μm PVDF syringefilter, ZnO sol-gel was spin-coated onto the top of the ITO substrate at5000 rpm for 30 s (acceleration 5000 rpm). The substrate was annealed at170° C. in air for 15 min and taken into glove box for deposition of theactive layer. At the same time, 10 mg of P(BDT-FTT) and 16 mg of PC₇₀BMwere mixed in ortho-xylene (1 mL) and stirred at 100° C. for 12 h.Diiodooctane (25 μL) was added to the solution and stirred for anadditional 1 h, followed by filtration through a 0.45 μm PTFE syringefilter. Afterwards, the solution was coated on the substrate at 1,800,2,000, and 2,200 rpm for 20 s. The substrate was solvent annealed insideof glass dishes for 1 h. After solvent annealing, the substrate wasscratched at the edge to expose the ITO layer for the metal deposition.The substances were placed in the metal evaporator, and 14 nm of MoO₃and 100 nm of Ag were deposited. The deposition speed for the MoO₃ was0.5 Å/s. The deposition speed for Ag started at 0.5 Å/s until 5 nm wasdeposited. Afterward, the speed increased to 1-1.5 Å/s until 100 nm wasdeposited. The devices were encapsulated using UV-curable epoxy and acover glass, and exposed to UV cure for 10 min.

The current density-voltage (J-V) curves were measured using a Keithley2400 source meter. The photocurrent was measured under AM 1.5 Gillumination at 100 mW/cm² under Newport Thermal Oriel 91192 1000 Wsolar simulator (4″×4″ beam size). The light intensity was calibrated bya mono-silicon detector (with KG-5 visible color filter) calibrated byNational Renewable Energy Laboratory to minimize spectral mismatch.

Table 1 depicts the solar cell performance of polymers from Examples1-6.

FTT(E):FTT(P) V_(oc) J_(sc) Fill PCE R_(s) R_(sh) Examples ratio (V)(mA/cm²) Factor (%) (%) (Ω · cm²) (Ω) 1 0:1 0.740 17.3 62.4 7.99 4.65723 2 0.3:0.7 0.75 16.5 65.0 8.07 4.6 9412 3 0.5:0.5 0.77 16.5 70.18.90 3.4 9286 4 0.7:0.3 0.76 16.1 61.1 7.48 5.0 5547 5 0.9:0.1 0.80 14.565.5 7.60 5.2 7567 6 1:0 0.80 16.0 68.6 8.74 4.1 10504

Table 2 depicts the solar cell performance of polymers from Examples7-9.

FTT(E):FTT(K1) V_(oc) J_(sc) Fill PCE R_(s) R_(sh) Polymer ratio (V)(mA/cm²) Factor (%) (%) (Ω · cm²) (Ω · cm²) Example 7 0.25:0.75 0.8115.89 59.95 7.72 7.25 620 8 0.5:0.5 0.77 17.29 64.79 8.26 5.19 779 90.75:0.25 0.79 16.83 67.84 9.04 4.34 815

Table 3 depicts the solar cell performance of polymers from Example 10.

FTT(E):FTT(K2) V_(oc) J_(sc) Fill PCE R_(s) R_(sh) Polymer ratio (V)(mA/cm²) Factor (%) (%) (Ω · cm²) (Ω · cm²) Example 10 0.5:0.5 0.79 17.368 9.30 2.8 956

Table 4 depicts the solar cell performance of polymers from Example 11.

FTT(P):FTT(K1) V_(oc) J_(sc) Fill PCE R_(s) R_(sh) Polymer ratio (V)(mA/cm²) Factor (%) (%) (Ω · cm²) (Ω · cm²) Example 11 0.5:0.5 0.8115.77 63.49 8.11 4.97 713

Example 12

The polymer derivative of example 3 was further optimized in devices. Adevice structure was used which included a [6,6]-phenyl C61 butyric acid2-hydroxyethyl ester (PCBE-OH) doped ZnO film as a interfacial layer.The resulting solar cell performance is depicted in FIG. 1 and Table 5below. The V_(oc) for this device slightly higher compared to the abovefabrication method, and the J_(sc) increases to 17.4 mA/cm².

TABLE 5 V_(oc) J_(sc) Fill PCE R_(s) R_(sh) Polymer Device Structure (V)(mA/cm²) Factor (%) (%) (Ω · cm²) (Ω · cm²) Example 3 ITO/ZnO/ZnO- 0.7917.4 69.0 9.46 3.7 731 PCBOH/active layer/MoO₃/Ag

TABLE 6 Monomer ratio V_(oc) J_(sc) FF PCE Polymer FTTM FTTE BDTE (V)(mAcm⁻²) (%) (%) Example 6 0 100 100 0.80 15.2 68.8 8.38 Example 12 2575 100 0.78 14.6 62.7 7.12 Example 13 50 50 100 0.77 16.6 72.1 9.15Example 14 75 25 100 0.72 16.8 58.7 7.18

In closing, it should be noted that the discussion of any reference isnot an admission that it is prior art to the present invention,especially any reference that may have a publication date after thepriority date of this application. At the same time, each and everyclaim below is hereby incorporated into this detailed description orspecification as an additional embodiment of the present invention.

Although the systems and processes described herein have been describedin detail, it should be understood that various changes, substitutions,and alterations can be made without departing from the spirit and scopeof the invention as defined by the following claims. Those skilled inthe art may be able to study the preferred embodiments and identifyother ways to practice the invention that are not exactly as describedherein. It is the intent of the inventors that variations andequivalents of the invention are within the scope of the claims whilethe description, abstract and drawings are not to be used to limit thescope of the invention. The invention is specifically intended to be asbroad as the claims below and their equivalents.

The invention claimed is:
 1. A polymer having two different sets ofrepeat units consisting essentially of:

wherein the two sets of repeat units are abenzo[1,2-b:4,5-b′]dithiophene with a 2-ethylhexyl substituted3-fluorothieno[3,4-b]thiophene and a benzo[1,2-b:4,5-b ′]dithiophenewith a propyl substituted 3-fluorothieno[3,4-b]thiophene


2. The polymer of claim 1, wherein the aryl groups comprise ofheterocycles and fused heterocycles.
 3. The polymer of claim 1, whereinthe polymer is regio-regular.
 4. The polymer of claim 1, wherein thepolymer is regio-random.
 5. The polymer of claim 1, wherein the polymeris used as photovoltaic material in one or more photovoltaic devices. 6.The polymer of claim 5, wherein the one or more photovoltaic devices arepolymer solar cell devices or photodetector devices.
 7. The polymer ofclaim 1, wherein the polymer is used as active layer material in one ormore electronic devices.
 8. The polymer of claim 7, wherein the one ormore electronic devices are field effect transistors, light emittingdevices, and sensors, electrochromic devices and capacitors.
 9. Thepolymer of claim 1, wherein the ratio of

in the polymer is around 50:50.
 10. The polymer of claim 1, wherein thetwo sets of repeat units are a benzo[1,2-b:4,5-b′]dithiophene with a2-ethylhexyl substituted 3-fluorothieno[3,4-b]thiophene and abenzo[1,2-b:4,5-b′]dithiophene with a propyl substituted3-fluorothieno[3,4-b]thiophene in a ratio of around 50:50.
 11. A polymerhaving two different sets of repeat units consisting essentially of:

wherein the two sets of repeat units are a2-ethyl-1-(3-fluorothieno[3,4-b]thiophen-2-yl)hexan-1-one and a1-(3-fluorothieno[3,4-b]thiophen-2-yl)butan-1-one